I want to be able to intercept and reject a request through the proxy by examining body content. For example, my request coming through is a grapql query or mutation in ``body`` of ``POST`` ```` mutation { registerUser ( ... ) { ... } } ```` and I want to be able to examine the content body for ``registerUser`` (or something else) and reject with a ``403 - Forbidden``. I feel it's similar, but the opposite to here: https://github.com/chimurai/http-proxy-middleware/issues/97 So I'd like to use ``onProxyReq``, but I dont' know how to read the body and then make an action using ``req`` / ``res``. Anyone can help?